fix: make babel dependencies optional (fixes #38)

* fix default config to only require babel-loader and @babel/preset-env if there is no override

* remove references to jsx

* move babel deps to optional dependencies

* fix formatting / add comments about optional babel deps

* lazy-load default options so that babel deps don’t need to be installed

Author: silbinarywolf

README.md

@@ -71,7 +71,7 @@ Object of webpack options. Just `require` in the options from your `webpack.conf
   module: {
     rules: [
       {
-        test: /\.jsx?$/,
+        test: /\.js?$/,
         exclude: [/node_modules/],
         use: [{
           loader: 'babel-loader',

index.js

@@ -7,25 +7,31 @@ const createDeferred = require('./deferred')
 
 const bundles = {}
 
-// by default, we transform JavaScript (up to anything at stage-4) and JSX
-const defaultOptions = {
-  webpackOptions: {
-    module: {
-      rules: [
+// by default, we transform JavaScript supported by @babel/preset-env
+const defaultBabelLoaderRules = () => {
+  return [
+    {
+      test: /\.js?$/,
+      exclude: [/node_modules/],
+      use: [
         {
-          test: /\.jsx?$/,
-          exclude: [/node_modules/],
-          use: [
-            {
-              loader: require.resolve('babel-loader'),
-              options: {
-                presets: [require.resolve('@babel/preset-env')],
-              },
-            },
-          ],
+          loader: require.resolve('babel-loader'),
+          options: {
+            presets: [require.resolve('@babel/preset-env')],
+          },
         },
       ],
     },
+  ]
+}
+
+// we don't automatically load the rules, so that the babel dependencies are
+// not required if a user passes in their own configuration
+const defaultOptions = {
+  webpackOptions: {
+    module: {
+      rules: [],
+    },
   },
   watchOptions: {},
 }
@@ -63,6 +69,11 @@ const preprocessor = (options = {}) => {
 
     // user can override the default options
     let webpackOptions = Object.assign({}, defaultOptions.webpackOptions, options.webpackOptions)
+    // here is where we load the default rules if the user has not passed
+    // in their own configuration
+    if (webpackOptions.module.rules === defaultOptions.webpackOptions) {
+      webpackOptions.module.rules = defaultBabelLoaderRules()
+    }
     let watchOptions = Object.assign({}, defaultOptions.watchOptions, options.watchOptions)
 
     // we're provided a default output path that lives alongside Cypress's
@@ -173,7 +184,15 @@ const preprocessor = (options = {}) => {
   }
 }
 
-// provide a clone of the default options
-preprocessor.defaultOptions = cloneDeep(defaultOptions)
+// provide a clone of the default options, making sure to lazy-load
+// babel dependencies so that they aren't required unless the user
+// utilizes them
+Object.defineProperty(preprocessor, 'defaultOptions', {
+  get () {
+    const clonedDefaults = cloneDeep(defaultOptions)
+    clonedDefaults.webpackOptions.module.rules = defaultBabelLoaderRules()
+    return clonedDefaults
+  },
+})
 
 module.exports = preprocessor

package.json

@@ -59,10 +59,12 @@
     "webpack": "^4.18.1"
   },
   "peerDependencies": {
+    "webpack": "^4.18.1"
+  },
+  "optionalDependencies": {
     "@babel/core": "^7.0.1",
     "@babel/preset-env": "^7.0.0",
-    "babel-loader": "^8.0.2",
-    "webpack": "^4.18.1"
+    "babel-loader": "^8.0.2"
   },
   "dependencies": {
     "bluebird": "3.5.0",